Feedback catastrophe

This fine balance between the protection and destruction of the processes maintaining life is a reminiscent of the catastrophe theory proposed by Rene Thom in the early 1970 s [323]. We are currently applying mathematical modelling to this biological feedback system in order to establish its relationship with the catastrophe hypothesis. 

In fermentations, as in other processes, early fault detection is needed to minimize the impact of such faults on the process and thus product quality. For fermentations, a drift in pH measurement that is part of the feedback control can be catastrophic. PLS scores can be used to detect and isolate fault sensors. Outlier conditions can be flagged, indicating that the process is operating outside of the conditions used to develop the... 

The Solar System is not stable, neither is our planet. Both are chaotic, in which luck may allow a certain degree of stasis. Thus orbital collisions occur until there are few bodies left, and interactions become so infrequent that the large planets seem to have attained stability in orbit. On a planet, geochemistry and heat production sort themselves out until the structure of the planet and its tectonic behaviour seem stable. But neither orbits nor tectonics are truly stable. Catastrophic events can and will occur that can upset the system. Planets collide. The Earth has precipitated a core, probably frozen a magma ocean, and will eventually freeze and be still. To stabilize the surface of a planet such that life can exist for 4Ga surely needs restorative feedbacks, and perhaps luck also. 

CMOS devices can develop a serious problem called latchup, in which junctions in different devices connect and form a forward-biased diode structure, leading to a catastrophic current which destroys the circuit. As illustrated in Fig. 14.5a, the latchnp is caused by the formation of a pnpn device between the terminal of VSS and VDD (see Chap. 9, Sect. 1.3). In a latchup condition, the pnpn device is biased snch that the collector current of the pnp bipolar transistor supplies a base current to the npn bipolar transistor in a positive feedback situation. The latchup can cause device function failure or even self-bumout. Figure 14.5b shows the bipolar components and resistive components of a latchup configuration. The conduction state of a pnp device requires Vq, and the conduction state... 

This includes also catastrophic events such as volcanic eruptions and the impaet of celestial bodies. It is beyond the focus of this book to describe the physics of sueh alterations. However, with an understanding of the chemical evolution of the eli-mate system (Chapter 2), it is evident that different chronological processes are superposed and that the different causes are interlinked in the sense of climatic feedbacks which make it very difficult to quantify climate changes and variations. Temperature and precipitation, as the most important climatic factors, are interrelated, but they are also interrelated with atmospheric composition and surface characteristics which again are interrelated. 

Although not a recommendation in the accident report, it can be speculated that this feedback system (which can cause a Catastrophic functional failure, see Section 1.3.6) is vulnerable to a common mode failure (see Chapter 6 Step la) and should have been provided by independent means. 

Non-emotive language was deliberately selected for providing feedback about hazards, for example words such as catastrophic or extreme were not used in the risk ranking labels. All case reports were de-identified to preserve the anonymity of the participants. Where elements were handled with expertise this was recognized and fed back to organization by giving it a risk ranking of zero - or well done . 

One of the most extensively elaborated methods for sharpening decisions is that of simulation. Simulation places the decision maker in situations that in certain important ways are similar to those they are likely to encounter in the real world. People are exposed to a rich variety of situations in which the consequences of an error are not bound to be catastrophic. Performance can be evaluated and immediate feedback be provided. On the negative side, simulation must be carefully designed to present the critical aspects of the real decision if proper transfer is to be obtained. Unforeseen, unique events cannot be simulated, though. For further discussion of simulation approaches see Nickerson Feehrer (1975). 

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